This invention relates to a thermosettable fiber reinforced resin composition containing thermosetting resins based on polyurethanes and unsaturated polyesters formed from poly(acrylates).
U.S. Pat. No. 3,700,752 describes a process for the preparation of shaped polymeric articles by gelpolymerizing a homogeneous composition comprising at least one vinyl monomer and the precursors of a cross-linked polyurethane and shaping the composition at a stage when it is still fluid, in which the composition comprises from 5 to 95% by weight of cross-linked polyurethane precursors free of groups copolymerizable with vinyl monomer and from 95 to 5% by weight at least one vinyl monomer, and the gellation of the resin via formation of the polyurethane is substantially completed before polymerization of the vinyl monomer is allowed to proceed to the extent that the vinyl polymer so produced forms a separate phase, and thereafter polymerization of the vinyl monomer is completed. The vinyl monomers are described as including esters of acrylic acid. The urethanes suitable for use in U.S. 3,700,752 are such that the cross-link density of these urethanes is lower than those of the present invention.
The patent states in column 12 that the notch impact strengths of the products produced can be improved by incorporating fibrous reinforcement in the product in proportions of 10 to 50% by weight of the total weight of the fiber-reinforced product.
The instant polyurethane/polyester resin systems are especially suited to produce thermoset molded articles by rapid injection molding techniques. The polyurethane/polyester resin systems of this inventin are not gelled via formation of the polyurethane prior to molding as the resins in U.S. Pat. No. 3,700,752.
U.S. Pat. No. 4,098,733 describes that polyurethanes and vinyl polymer composites are rapidly prepared without the requirement of the application of an external source of heat by the admixture of a composition comprising (A) a liquid polyol, (B) an organic polyisocyanate, (C) a liquid ethylenically unsaturated monomer, (D) a catalyst for polymerizing componet (C), (E) a caalyst for urethane formation, (F) 0 to 50% by weight based upon the combined weights of components (A), (B), (C), (D), (E) and (F) of a modifier substance. The modifier substances are stated, in column 2 of the patent, as selected from (1) liquid substances having an atomspheric boiling point of at least about 150.degree. C.; (2) solid substances having a surface area of less than about 0.8 m.sup.2 /gram and a particle size such that it will pass through a 1/4 inch square opening and will not decompose at a temperature below the maximum exotherm temperature generated by the urethane forming reaction; (3) particular polymers of one or more ethylenically unsaturated monomers and (4) mixtures thereof. Several provisos are then stated, one of which is that the combined quantity of components (C) and (F) be less than about 60% by weight based upon the combined weights of components (A), (B), (C) and (F).
The admixed composition is stated to be then poured into a suitable mold wherein the composition solidifies within about 15 minutes to a solid having a density of at least about 1 g/cc and a percent elongation of less than about 100.
Suitable components stated as component (F2), i.e., the solid substances, in the patent are described in column 11 as including sold modifiers such as the woven or mat materials wherein the individual fibers from which such materials are prepared have a surface area of less than 0.8 m.sup.2 /gram and which will pass through a 1/4 inch square opening.
Of the 87 Examples of this patent, only two Examples, i.e., Examples 10 and 11 describe an acrylate component. Example 10 of this patent describes blending the following components: 50 grams of Polyol A (defined in column 10 as an adduct of glycerine and propylene oxide, said adduct having an active hydrogen (OH) equivalent weight of about 87), 50 grams of Polyisocyanate A (defined in column 10 as an 80/20 mixture by weight of 2,4- and 2,6-toluenediisocyanate having an isocyanate equivalent weight of about 87), 50 grams of styrene, 50 grams of the trimethacrylate ester of trimethylol propane, 0.4 grams of tertiarybutyl perbenzoate and 1.14 grams of lead octoate. Example 11 describes blending the following components: 50 grams of Polyol A, 50 grams of polyisocyanate A, 50 grams of styrene, 24 grams of the dimethacrylate ester of 1,3-butylene glycol, 0.3 grams of tertiary butyl perbenzoate, and 1.14 grams of lead octoate.
Example 86 of this patent describes blending the following components: 50 grams of Polyol A, 50 grams of Polyisocyanate A, 50 grams of styrene, 1 gram of tertiary-butyl perbenzoate and 0.23 grams of lead octoate. The mixture is poured over 35 grams of glass fiber cloth having a surface area of &lt;0.3 m.sup.2 /grams. Only this Example of the patent describes a composition added to glass.
Therefore, according to U.S. Pat. No. 4,098,733 component (F) is optional and limited in its use since the composition can contain 0 to 50% by weight of this component. The amount of glass reinforcement which can be added is also constrained by limits on the total amount of polyester and component F in the composition. These limitations exclude those compositions which we have found to offer optimum mechanical properties. Also, this component (F) is described as selected from one of four components, i.e., (1) to (4), supra, with only one Example describing glass fiber cloth.
In the instant invention, it has been found that thermosetting resins based on polyurethane and unsaturated polyesters formed from poly(acrylates), containing fiber reinforcement produce molded articles with an excellent combination of mechanical properties. Composites prepared from the polyurethane and unsaturated polyester resins of this invention have a combination of physical properties superior to those of composites prepared from either polyester resins or polyurethane resins.